Because of this, my FL9 sat in a drawer for the best part of a year. It's an old pedal (over 25 years) and the last time I went to use it, it just passed a clean tone. The pedal wasn't toally broken, the delay chip was still working as there as a bit of a flange sound when twiddling the controls. Upon opening it up, some of the jooints looked cold. So I proceeded to re-solder everything on the board. No go. It took a while to track down the schematic (didn't end up using it), but I'd read a snippet from one forum about replacing old electrolytic caps, so i figured that i'd give it a try. I went over the board and documented everything electrolytic.
There were two caps near the middle of the board which weren't coloured blue like the rest (they were orange), so I decided to replace them first and give it a test (I'd seen a similar arrangement on a synth I'd built). My hunch was right, they were there to control the LFO rate. The LFO was working again, but the effect was very subtle. Not at all like I remembered.
Fortunately the board has three trim pots for adjusting various biases. Ignore the middle one, it's there to bias a transistor and the factory setting is just right to avoid unwanted and unpleasant clipping. The trim pot closes to the middle controls feedback and the one further away controls depth. With these two trim pots you can get the pedal to self oscillate. Particularly with the first one. It's not a sound I'd want all the time, so I've set it up to kick in at about 70% maximum on the front panel feedback knob. The mod is safe and easy to do. You won't even need to take the board out to do it. While increasing the feedback makes the flanger more prominent, it still falls short of being a true "jet" flanger. Still it is nice to have in the tool kit.
|FL9 Service Manual Page 1|
|FL9 Service Manual Page 2 (Schematic)|
|FL9 Service Manual Page 3 (Trouble Shooting)|
|FL9 Service Manual Page 4 (PCB Layout) - LFO Caps Highlighted w/red box.|